Referring to drawings, description will be given of a basic configuration of a conventional and typical portable telephone. FIG. 1 shows a conventional portable telephone in a state in which a battery pack is installed therein, and (a) is a side view and (b) is a rear view. FIG. 2 shows the conventional portable telephone in a state in which the battery pack is removed therefrom, and (a) is a front view, (b) is a cross-sectional view, and (c) is a rear view.
As shown in FIGS. 1(a) and 1(b) and FIG. 2(a), the conventional and typical portable telephone 201 includes a main section 202 including an outer housing; and in the main section 202, a printed circuit board 203 on which a radio circuit, a control circuit (not shown), and the like are mounted is integrally disposed; and an antenna 204 electrically connected to the radio circuit is disposed on an end section side of the circuit board 203.
In the main section 202, a liquid crystal display section 205 and a keypad section 206 are disposed in a front surface side thereof as shown in FIG. 2(a); and an installation depression section 212 in which a battery pack 220 is attachably and detachably installed is disposed on a rear surface side as shown in FIG. 2(c). The depression section 212 is ordinarily formed to be substantially equal in an outer size and a contour to the battery pack 220 such that the pack 220 is just completely housed therein. In the depression section 212, there are disposed a set of power source pins 207 to be electrically connected to electrode terminals 227, which will be described later, on the battery pack 220 side.
Each power source pin 207 is electrically connected to a power source line or ground (not shown) formed on the printed circuit board 203. And at installation of the battery pack 220, two power source pins 207 are respectively connected to the respective electrode terminals (a positive electrode terminal and a negative electrode terminal) of the battery pack 220 such that power source (direct current) is supplied from the battery pack 220 to the circuit board 203.
FIGS. 3 and 4 show a battery pack: FIG. 3(a) is a disassembled view; FIG. 3(b) is a perspective view; FIG. 4(a) is a front cross-sectional view; FIG. 4(b) is a side cross-sectional view; FIG. 4(c) is a bottom view.
As shown in FIGS. 3 and 4, the conventional and typical battery pack 220 includes a case 222 formed using a plastic, a mold resin, or the like, a battery can 221 formed using metallic material such as aluminum and an alloy, and the electrode terminals 227 (a positive electrode terminal and a negative electrode terminal) to obtain the power source. In this regard, a protective circuit and the like, not shown, are also mounted on the battery pack 220.
The case 222 is subdivided into a pair of a first shell 222a and a second shell 222b, and case structure is formed by engaging these first and second shells 222a and 222b with each other or by joining the shells 222a and 222b with each other by an adhesive or the like. And the battery can 221, the electrode terminals 227, and the protective circuit described above are housed in the case 222 to configure the battery pack 220.
As shown in FIGS. 3(a) and 4(a), for the power source of the battery pack 220, there has been disclosed a configuration in which positive potential and negative potential generated in the battery can 221 are obtained via the respective electrode terminals 227 (a positive electrode terminal and a negative electrode terminal) electrically connected to connection leads (reference is to be made to, for example, patent document 1). For example, in the configuration of a lithium ion battery, the battery can is a positive electrode (positive direct-current potential), but the positive electrode terminal is directly connected via the connection lead 228 to the battery can 221. Incidentally, as shown in FIGS. 4(a) and 4(b), the respective electrode terminals 227 are arranged in a depression section 222c disposed on an end surface of the case 222 and are placed at inner positions lower than the end surface of the case 222.
As already shown in FIG. 1, in the portable telephone 201 in a state in which the battery pack 220 is appropriately housed to be installed in the installation depression section 212, when the electrode terminals 227 on the battery pack 220 side are connected to the power source pins 207 on the main section 202 side with polarity matched therebetween, power is supplied from the battery pack 220 to the printed circuit board 203.
In this regard, the main section providing the installation depression section 212 in which the battery pack 220 is installed and the outer housing is generally formed using a non-metallic material, for example, a plastic or a mold resin to secure the insulation state with respect to the battery pack 220.    Patent Document 1: Japanese Patent Laid-Open Pub. No. 2003-249208    Patent Document 2: Japanese Patent Laid-Open Pub. No. 2003-348202